Transparent background WKWebView (NSView)

Question

I am building a Mac application using Swift. Therefor, I want to make a WKWebView transparent, so it shows the text of the loaded HTML, but the background of my underlaying NSWi

Answer 1

Updated, slightly better solution (2021). Use private property drawsBackground on WKWebViewConfiguration. It's property has been introduced in macOS 10.14 so it won't go away.

//https://opensource.apple.com/source/WebKit2/WebKit2-7610.2.11.51.8/UIProcess/API/Cocoa/WKWebViewConfigurationPrivate.h.auto.html
@property (nonatomic, setter=_setDrawsBackground:) BOOL _drawsBackground WK_API_AVAILABLE(macos(10.14), ios(12.0));

let configuration = WKWebViewConfiguration()
var requiresDrawBackgroundFallback = false
if #available(OSX 10.14, *) {                         
    configuration.setValue(false, forKey: "sward".reversed() + "background".capitalized) //drawsBackground KVC hack; works but private
} else {
    requiresDrawBackgroundFallback = true
}
let webView = WKWebView(frame: .zero, configuration: configuration)
if requiresDrawBackgroundFallback {
    webView.setValue(false, forKey: "sward".reversed() + "background".capitalized) //drawsBackground KVC hack; works but private
}